1. Field of the Invention
The invention is related to the field of printing systems, and in particular, to a high speed printing system for printing magnetic ink.
2. Statement of the Problem
Magnetic Ink Character Recognition (“MICR”) is a technology that allows a machine to read characters printed on a print medium. For example, the bottom line of a check is typically printed using a MICR ink so that the check can be processed automatically by a machine. Traditionally, a magnetic ink is printed using an offset printing press in which an inked image (that has the magnetic ink) is first transferred/offset to a rubber blanket, and then from the rubber blanket to paper. Many types of document production have recently moved to using high speed printing systems that are more customizable than the offset printing press. Such high speed printing systems usually use inkjet technologies to produce full colored documents.
Full colored documents are typically produced using inkjet technologies by ejecting varying amounts of inks of four colors: cyan, magenta, yellow, and black. Either dye-based inks or pigment-based inks are usually used. Meanwhile, a magnetic ink used for MICR printing is usually a hybrid ink with dye colorant and ferrite particles. However, it is generally believed that inks of different types should not be mixed. A dye-based ink has dye colorant, while a pigment-based ink has colored particles. Mixing them may cause undesired chemical reactions and/or plug up the nozzles (a printhead has a number of nozzles for ejecting ink from the printhead onto paper).
To reduce the possibility of mixing the magnetic ink with another ink, the magnetic ink is usually ejected from an additional printhead that is separate from the printhead(s) used for regular color printing. However, adding an additional printhead adds complexities to the printing systems, which is not desirable. Some high speed printing systems also use a series of printheads arranged in a column so that a large area of the print medium can be covered simultaneously. Retrofitting such high speed printing systems is even more difficult and costly because a series of printheads for printing the magnetic ink would need to be added.
Additionally, these high speed printing systems may eject inks of more than one color concurrently from each printhead to speed up printing. However, as more than one ink is ejected from each printhead with possible mixing of the inks, it is generally believed that all inks need to be switched to the same pigment-based type because the magnetic ink, with its ferrite particles, is more akin to a pigment-based ink. However, it would not be practical to completely switch from a dye-based printing system to a pigment-based printing system whenever the printing system needs to print the magnetic ink.